Synthesis and biological evaluation of methylated scutellarein analogs based on metabolic mechanism of scutellarin in vivo.

Scutellarin (1) could be hydrolyzed into scutellarein (2) in vivo and then converted into methylated, sulfated and glucuronidated forms. In order to investigate the biological activities of these methylated metabolites, eight methylated analogs of scutellarein (2) were synthesized via semi-synthetic methods. The antithrombotic activities of these compounds were evaluated through the analyzation of prothrombin time (PT), activated partial thromboplastin time (APTT), thrombin time (TT) and fibrinogen (FIB). Their antioxidant activities were assessed by measuring their scavenging capacities toward 1,1-diphenyl-2-picrylhydrazyl radical (DPPH) and the ability to protect PC12 cells against H2O2-induced cytotoxicity. Furthermore, the physicochemical properties of these compounds including aqueous solubility and lipophilicity were also investigated. The results showed that 6-O-methylscutellarein (5) demonstrated potent antithrombotic activity, stronger antioxidant activity and balanced solubility and permeability compared with scutellarin (1), which warrants further development of 5 as a promising lead for the treatment of ischemic cerebrovascular disease.